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Testing If Vct Is Working Properly

Chi100188

By Chi100188,
in Engines & Forced Induction

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Chi100188 Mentor

Chi100188

Posted
  • Author
Posted

well last week i was getting car tuned had a few problems in the past such as cas,coil packs, exhaust cam gear set on 2 degrees retard all been fixed now and the car still wouldn't make any power down low until 5k rpm the power would just shoot up so the tuner reckon it was the VCT not work so i changed the solonoid but i want to test if the vct is really work or not

PM-R33 Grand Master

PM-R33

Posted
Posted (edited)

First thing do this:

1. Start car

2. Remove plug from VCT solenoid

3. Set up test light onto VCT solenoid plug

4. Get some one to put car into gear (obviously holding the clutch in) and rev the car

The test light should light up above the 1200ish rpm and stay lit until the 4500ish rpm. This will tell you that the ECU is actually giving power to the solenoid.

The only way now is to put it onto a dyno and do two runs back to back plotted on top of one another. One with the VCT plugged in, one with it unplugged. If both runs are identical you know you have a problem with the solenoid itself. It is pretty rare to have a solenoid fail though.

Edited by PM-R33
Messiah Mentor

Messiah

Posted
Posted

or poor mans seat of the pants approach.

Give it a bootful in low gear to 4k rpm with vct plugged, ensure you stay below the speed limit.

step 2.

Unplug vct and repeat, if run two feels like arse... vct is working ok in run one. if they feel the same... vct is broken

Kaido_RR Grand Master

Kaido_RR

Posted
Posted
  robbo_rb180 said:
what ecu are you using? may have to setup vct as an output.

Its running a PFC.

we have have heaps of issue with the car and has been to the tuners now 3times and still no complete tune, so the owner is getting abit dishearten hence why we want to work out if the VCT is working.

We did a swap yesterday using the old VCT solenoid from my old engine, however we are not 100% sure if the solenoid was the problem or if we needed to swap the cam gear aswell

RRob Community Regular

RRob

Posted
Posted
  Sheriff Wan said:
You should be able to hear the solenoid click when you pull the throttle when under the bonnet, this would suggest it is working... It's a noticeable noise

The car has to be in gear(just not in neutral) for this to work.

Chi100188 Mentor

Chi100188

Posted
  • Author
Posted

so i pretty much sit in the car put it in first clutch in rev it till 4000 rpm to and get another person to have his ear in the engine bay to hear a click or not or alternatively just drive the car with the vct plug in then take it out and see how the drive is after that?

  • 2 weeks later...
Rolls Grand Master

Rolls

Posted
Posted

Where is the VCT solenoid in the engine bay? Also when does it switch on, 1500 - 4000 rpm? or is it 5000 rpm.

Just got my eboost street and it has a window aux function which I am planning on using to control my VCT.

Also does the VCT activate when you ground the relay, or provide power to it?

Cheers

  • 1 year later...
urtwhistle Proficient

urtwhistle

Posted
Posted

Hey guys I'm wondering if I have potential problems with VCT on my R34 also.

I have tried testing it as well as I can until it goes on a dyno, so please give me your thoughts.

I removed the VCT plug and applied power directly to the solenoid and it clicked as it should have. I measured the voltage at the plug @ idle and it had 10v but I couldn't get it to trigger and go any higher.

I tried setting the power fc trigger points at 0 4500 and 7400rpm and 7400 gave the best boost response for some reason.

I also tried driving around with it plugged in and unplugged and there was no difference.

Rolls Grand Master

Rolls

Posted
Posted (edited)

You need to put it on a dyno and wire it on all the time, do a power run, then unplug it and do another dyno run.

Now overlay the two graphs, where the graph with it permanently on dips below the graph with it always off should be your ultimate switch over point. Doing anything other than this is guessing and will give sub optimal results.

53948234.jpg

edit it is possible the solenoid is jammed, I had to hit mine with a hammer and then pulse it on and off 10 times to get it to start clicking.

Edited by Rolls

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